Since the discovery of the piezoelectric effect, many types of mechanical-electrical measuring transducers based on this effect have been produced, in particular force and pressure transducers and accelerometers. The compactness, high rigidity and high resonant frequency of piezoelectric type accelerometers render such accelerometers excellent instruments to measure various inertial forces as disclosed in U.S. Pat. Nos. 4,227,198; 4,088,027; 5,299,075 and 4,016,437.
In U.S. Pat. No. 4,227,198, a piezoelectric accelerometer measures seismic activity caused by explosives in a mining operation. That accelerometer comprises a seismic sensor, delay circuitry, an amplifier, a comparator and a recorder. The seismic sensor generates a sensor signal in response to any seismic activity. The amplifier receives and amplifies the sensor signal. The comparator and the delay circuitry receive the amplified sensor signal. The comparator determines if sensor signal has reached a predetermined threshold. When the threshold is reached, the comparator generates a threshold signal. The recorder receives the threshold signal and turns on to record the sensor signal that will be released from the delay circuitry, otherwise the sensor signal is not recorded. Thus, the accelerometer is designed to accurately record a particular frequency range of forces.
The capability of accelerometers have been explored to measure various inertial forces. However, accelerometers have not previously been used to accurately monitor and record all frequency inertial forces by adjusting the accelerometer's sensitivity in response to the strength of inertial forces. The present invention is designed to resolve this inadequacy.
In addition to altering the sensitivity of the accelerometer, the proposed accelerometer would allow civil engineers to monitor inertial forces applied to a civil engineering structure to determine the safety of the structure.